---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/vegalite/v5/api.py in ?(self, include, exclude)
   2154         # see https://github.com/ipython/ipython/issues/11038
   2155         try:
   2156             dct = self.to_dict()
   2157         except Exception:
-> 2158             utils.display_traceback(in_ipython=True)
   2159             return {}
   2160         else:
   2161             return renderers.get()(dct)

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/vegalite/v5/api.py in ?(self, *args, **kwargs)
    846 
    847         # TopLevelMixin instance does not necessarily have to_dict defined
    848         # but due to how Altair is set up this should hold.
    849         # Too complex to type hint right now
--> 850         dct = super(TopLevelMixin, copy).to_dict(*args, **kwargs)  # type: ignore[misc]
    851 
    852         # TODO: following entries are added after validation. Should they be validated?
    853         if is_top_level:

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(self, validate, ignore, context)
    792                 k: v for k, v in kwds.items() if k not in list(ignore) + ["shorthand"]
    793             }
    794             if "mark" in kwds and isinstance(kwds["mark"], str):
    795                 kwds["mark"] = {"type": kwds["mark"]}
--> 796             result = _todict(
    797                 kwds,
    798                 context=context,
    799             )

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
    338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):
--> 340         return {k: _todict(v, context) for k, v in obj.items() if v is not Undefined}
    341     elif hasattr(obj, "to_dict"):
    342         return obj.to_dict()
    343     elif isinstance(obj, np.number):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(.0)
--> 340 def _todict(obj, context):
    341     """Convert an object to a dict representation."""
    342     if isinstance(obj, SchemaBase):
    343         return obj.to_dict(validate=False, context=context)

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    334     """Convert an object to a dict representation."""
    335     if isinstance(obj, SchemaBase):
    336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
--> 338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):
    340         return {k: _todict(v, context) for k, v in obj.items() if v is not Undefined}
    341     elif hasattr(obj, "to_dict"):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(.0)
--> 338 def _todict(obj, context):
    339     """Convert an object to a dict representation."""
    340     if isinstance(obj, SchemaBase):
    341         return obj.to_dict(validate=False, context=context)

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    333 def _todict(obj, context):
    334     """Convert an object to a dict representation."""
    335     if isinstance(obj, SchemaBase):
--> 336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
    338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/vegalite/v5/api.py in ?(self, *args, **kwargs)
   2516             # for easier specification of datum encodings.
   2517             copy = self.copy(deep=False)
   2518             copy.data = core.InlineData(values=[{}])
   2519             return super(Chart, copy).to_dict(*args, **kwargs)
-> 2520         return super().to_dict(*args, **kwargs)

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/vegalite/v5/api.py in ?(self, *args, **kwargs)
    846 
    847         # TopLevelMixin instance does not necessarily have to_dict defined
    848         # but due to how Altair is set up this should hold.
    849         # Too complex to type hint right now
--> 850         dct = super(TopLevelMixin, copy).to_dict(*args, **kwargs)  # type: ignore[misc]
    851 
    852         # TODO: following entries are added after validation. Should they be validated?
    853         if is_top_level:

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(self, validate, ignore, context)
    792                 k: v for k, v in kwds.items() if k not in list(ignore) + ["shorthand"]
    793             }
    794             if "mark" in kwds and isinstance(kwds["mark"], str):
    795                 kwds["mark"] = {"type": kwds["mark"]}
--> 796             result = _todict(
    797                 kwds,
    798                 context=context,
    799             )

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
    338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):
--> 340         return {k: _todict(v, context) for k, v in obj.items() if v is not Undefined}
    341     elif hasattr(obj, "to_dict"):
    342         return obj.to_dict()
    343     elif isinstance(obj, np.number):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(.0)
--> 340 def _todict(obj, context):
    341     """Convert an object to a dict representation."""
    342     if isinstance(obj, SchemaBase):
    343         return obj.to_dict(validate=False, context=context)

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    333 def _todict(obj, context):
    334     """Convert an object to a dict representation."""
    335     if isinstance(obj, SchemaBase):
--> 336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
    338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(self, validate, ignore, context)
    792                 k: v for k, v in kwds.items() if k not in list(ignore) + ["shorthand"]
    793             }
    794             if "mark" in kwds and isinstance(kwds["mark"], str):
    795                 kwds["mark"] = {"type": kwds["mark"]}
--> 796             result = _todict(
    797                 kwds,
    798                 context=context,
    799             )

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
    338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):
--> 340         return {k: _todict(v, context) for k, v in obj.items() if v is not Undefined}
    341     elif hasattr(obj, "to_dict"):
    342         return obj.to_dict()
    343     elif isinstance(obj, np.number):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(.0)
--> 340 def _todict(obj, context):
    341     """Convert an object to a dict representation."""
    342     if isinstance(obj, SchemaBase):
    343         return obj.to_dict(validate=False, context=context)

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    334     """Convert an object to a dict representation."""
    335     if isinstance(obj, SchemaBase):
    336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
--> 338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):
    340         return {k: _todict(v, context) for k, v in obj.items() if v is not Undefined}
    341     elif hasattr(obj, "to_dict"):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(.0)
--> 338 def _todict(obj, context):
    339     """Convert an object to a dict representation."""
    340     if isinstance(obj, SchemaBase):
    341         return obj.to_dict(validate=False, context=context)

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/utils/schemapi.py in ?(obj, context)
    333 def _todict(obj, context):
    334     """Convert an object to a dict representation."""
    335     if isinstance(obj, SchemaBase):
--> 336         return obj.to_dict(validate=False, context=context)
    337     elif isinstance(obj, (list, tuple, np.ndarray)):
    338         return [_todict(v, context) for v in obj]
    339     elif isinstance(obj, dict):

/opt/hostedtoolcache/Python/3.10.15/x64/lib/python3.10/site-packages/altair/vegalite/v5/schema/channels.py in ?(self, validate, ignore, context)
     43                 # We still parse it out of the shorthand, but drop it here.
     44                 parsed.pop('type', None)
     45             elif not (type_in_shorthand or type_defined_explicitly):
     46                 if isinstance(context.get('data', None), pd.DataFrame):
---> 47                     raise ValueError(
     48                         'Unable to determine data type for the field "{}";'
     49                         " verify that the field name is not misspelled."
     50                         " If you are referencing a field from a transform,"

ValueError: Unable to determine data type for the field "ln"; verify that the field name is not misspelled. If you are referencing a field from a transform, also confirm that the data type is specified correctly.